Inform Clang that TLS is implemented by LLVM for RISC-V
|(On Diff #182916)
With the exception of SystemZTargetInfo, all CPU target info classes rely on the base already initialising it to true by default, so you can just delete this line.
Could you add a test for this? I'm not sure if this is best done with a test that uses __has_feature or otherwise (I note other targets don't seem to have similar tests currently), but I think it would be handy.